S. K. Kakoty

Effect of Fluid Inertia on Stability of Oil Journal Bearings

In the analysis of hydrodynamic journal bearings the effect of fluid inertia is generally neglected in view of its negligible contribution compared to viscous forces. However, the fluid inertia effect is to he taken in the analysis when modified Reynolds number is around one. Though there are a few attempts to analyse steady-state and dynamic characteristics of finite journal bearings, stability of the journal under the effect of fluid inertia is yet to he investigated. An attempt has been made to evaluate the mass parameter (a measure of stability) besides finding out the steady-state characteristics of finite journal bearings considering the effects of fluid inertia. The analysis is carried out for modified Reynolds number ∼O(l.), which is assumed to be laminar. A nonlinear time transient analysis is carried out for the stability analysis.

Optimum Groove Location of Hydrodynamic Journal Bearing Using Genetic Algorithm

This paper presents the various arrangements of grooving location of two-groove oil journal bearing for optimum performance. An attempt has been made to find out the effect of different configurations of two groove oil journal bearing by changing groove locations. Various groove angles that have been considered are 10°, 20°, and 30°. The Reynolds equation is solved numerically in a finite difference grid satisfying the appropriate boundary conditions. Determination of optimum performance is based on maximization of nondimensional load, flow coefficient, and mass parameter and minimization of friction variable using genetic algorithm. The results using genetic algorithm are compared with sequential quadratic programming (SQP). The two grooved bearings in general have grooves placed at diametrically opposite directions. However, the optimum groove locations, arrived at in the present work, are not diametrically opposite.

Analysis of dimple textured parallel and inclined slider bearing

Textured slider bearing is of immense interest from some time now. The present study takes up both parallel and inclined slider bearing with dimple textured surface. Simple solution scheme is adopted to obtain non-dimensional load-carrying capacity of fully textured and partially textured slider bearings. When bearing with aspect ratio (length-to-width ratio) less than unity performs better with full texturing, while partial texturing performs better for higher aspect ratios. Optimum textured portion of slider width for different aspect ratios are provided. The effect of direction of texturing on the performance of textured slider bearing is investigated and it is observed that forward texturing has better performance than backward texturing.

Groove location for optimum performance of three- and four-lobe bearings using genetic algorithm

This paper presents the various arrangements of grooving location of three- and four-lobe oil journal bearing for optimum performance. An attempt has been made to find out the effect of different configurations of three- and four-lobe oil journal bearing by changing groove locations. The Reynolds equation is solved numerically in a finite difference grid satisfying the appropriate boundary conditions. Determination of optimum performance is based on maximization of non-dimensional load, flow coefficient and mass parameter and minimization of friction variable using genetic algorithm. The optimum groove locations arrived at are not at symmetrical position, which is the current practice. The present analysis is carried out and results are obtained for ellipticity ratio equal to 0.5.

Effect of Dam Depth and Relief Track Depth on Steady-State and Dynamic Performance Parameters of 3-Lobe Pressure Dam Bearing

The present study analyzes the effect of pressure dam depth and relief track depth on the performance of three-lobe pressure dam bearing. Different values of dam depth and relief track depth are taken in nondimensional form in order to analyze their effect. Results are plotted for different parameters against eccentricity ratios and it is shown that the effect of pressure dam depth and relief track depth has great significance on stability and other performance parameters. Study of stability and performance characteristics is undertaken simultaneously.

Groove Location for Optimum Performance of Two-Lobe Bearing UsingGenetic Algorithm

This paper presents the various arrangements of grooving location of two lobe oil journal bearing for optimum performance. An attempt has been made to find out the effect of different configurations of two lobe oil journal bearing by changing groove locations. Various groove angles that has been considered are 10°, 20° and 30°. The Reynolds equation is solved numerically in a finite difference grid satisfying the appropriate boundary conditions. Determination of Optimum performance is based on maximization of non dimensional load, flow coefficient and mass parameter and minimization of friction variable using Genetic Algorithm. The results using Genetic Algorithm are compared with Sequential quadratic programming (SQP). At optimum position there is a significant improvement in the optimum value of friction variable, flow coefficient, load and mass parameter value than that of two-lobe bearing with grooves position along horizontal direction and 1800 apart. The optimum groove locations arrived at are not diametrically opposite, which is the current practice. The present analysis is carried out and results are obtained for ellipticity ratio equal to 0.5.

Nonlinear Time Transient Stability Analysis of Multilobe Bearings

In some specialized applications, plain circular bearing is mostly replaced by some other bearings, as plain bearing does not suit the stability requirements of high-speed machines and precision machine tools. Grooved circular bearings and multi-lobe bearings with two lobes, three lobes and four lobes are commonly used. The present work gives insight into nonlinear transient analysis of multi lobe journal bearing systems. An attempt has been made to evaluate the critical mass parameter (a measure of stability) for various values of aspect ratios besides finding out the steady state characteristics of multilobe journal bearings (two grooved, two lobe, three lobe and four lobe) such as load bearing capacity, Sommerfeld number and attitude angle At moderate and heavy load conditions (Sommerfeld number from 0.1 to 0.3), four-lobe bearing is most stable. Three-lobe bearing is the best in the range of Sommerfeld number from 0.3 to 0.8. Two-lobe bearing is found to be more stable than other bearings beyond this range.Copyright

Stability Analysis of a Rigid Rotor Supported on Gas Foil Bearings Under Different Loading Conditions

Gas foil bearings (GFBs) has been considered as an alternative to traditional bearings in turbopumps, turbocompressors, and turbochargers. The popularity of this bearing has motivated the researchers and people from industries to explore its capabilities. In this context, a nonlinear transient analysis of a rigid rotor supported on airfoil bearing under unidirectional constant load and unidirectional periodic load is carried out. The nondimensional form of the Reynolds equation is discretized using Finite Difference Method while the Crank–Nicolson method and Newton–Raphson method are used to obtain the pressure at every time step. Mass parameter, which is a function of the speed of the rotor, has been considered as the parameter of stability. It has been observed that a rotor stable under unidirectional constant load can be unstable under unidirectional periodic load.

Load Capacity Analysis of Gas Foil Bearing (GFB) for Different Foil Materials

There is a significant attention on GFBs in recent times owing to its oil free technology and suitability over a wide array of operating conditions. However GFBs have considerably low load carrying capacity compared to normal GFBs. The present paper investigated the load capacity of the bump-type GFBs for a simple model considering only deflection of bump foils. The load capacity of GFBs with different foil materials has been inspected in view of comparing the load capacity. Also the variations of GFBs load performance with respect to the compliance of the foil have been reviewed.

Performance Analysis of Gas Foil Bearing with Different Foil Pivot Configuration

A numerical model is developed in order to find out the performance characteristics of gas foil bearings. The static performance analysis of gas foil bearings has been carried out using an elastic foundation model of the foil. The steady state results have been compared with the experimental and theoretical results available in the literature. The characteristics of the bearing have been investigated with change in foil pivot position. It has been shown that the load carrying capacity is different for different foil pivot positions. Besides effect of bearing parameters like eccentricity ratio, length to diameter ratio, compliance coefficient, and bearing number on the load carrying capacity with different foil pivot positions have been studied.